Drug-resistant leprosy: monitoring and current status.

Leprosy control depends solely on case detection and treatment with multi-drug therapy (MDT). – 3 This strategy is based on the principle that identifying and treating chronic infectious diseases with combinations of effective antibiotics limits the emergence and spread of new or existing antibiotic resistant pathogens. According to the World Health Organization (WHO), MDT formulated for leprosy has been effective at reducing both the prevalence and incidence of leprosy globally. – 5 According to official reports from 130 countries and territories, the global registered prevalence of leprosy at the beginning of 2011 was 192,246 cases, while the number of new cases detected during 2010 was 228,474. The most important indicator for the effectiveness of a chemotherapeutic regimen is the rate of relapse following successful completion of the scheduled course of treatment. Information from a number of leprosy control programmes suggests that the relapse rate is very low for both paucibacillary (PB) leprosy (0·1% per year) and multibacillary (MB) leprosy (0·06% per year). Lessons learned from tuberculosis strongly suggest that relapse cases are at risk for drug resistance and can undermine existing control measures. Therefore establishing the success of a strategy like MDT for leprosy control requires thorough evaluation of treatment failures, including drug susceptibility testing. Several studies have documented relapses after MDT – 14 and drug-resistant strains of Mycobacterium leprae have been identified. – 26 In contrast to what we know for tuberculosis, the current prevalence of primary and secondary resistance to rifampicin; dapsone, and clofazimine is virtually unknown for leprosy. Therefore, surveillance of drug resistance globally is a key factor in monitoring MDT effectiveness and preventing the spread of drug resistance. Over the past two decades, rapid DNA-based molecular assays for detection of drugresistant M. leprae directly from clinical specimens have been developed [Reviewed in]. Even though these assays are based on sophisticated, modern, molecular biology techniques, many reference laboratories in leprosy endemic countries have the capability of utilizing